The recognition strucures of both B cells and T cells have been examined using anti-receptor antibodies prepared against monoclonal anti-H-2 antibodies (mAb) and cytotoxic T cell (CTL) clones. Anti-idiotypic antibodies (anti-Id) were prepared against several monoclonal anti-H-2 antibodies. In one case, anti-idiotypic antibodies prepared against an anti-H-2Kb mAb detected a public idiotype expressed on a majority of anti-H-2Kb alloantibodies. In contrast, no reactivity could be detected between these anti-idiotypes and a series of cytotoxic T cell clones of a similar specificity. The results suggested that either the recognition structures of T cells and B cells are substantially different, the allo-determinants recognized by these cells are not the same, or the anti-idiotypes used did not detect appropriate idiotypes. To expand the idiotypic repertoire recognized by th anti-idiotypic reagents, rabbits were immunized with conventional anti-H-2Kb alloantibodies purified by affinity chromotography on an anti-28-13-3 Id column. These new anti-idiotypic reagents will be used to examine T cell recognition structures and to manipulate immune responses in vivo. In addition, anti-receptor antibodies specific for the CTL clones have been produced and attempts are being made to generate mAbs that recognize the T cell receptor.